Yes, the oil bath continued on 4wd V6 models up to 68-69, my 68 K2500 came with the same one Ed's 65 Suburban has which was made by Donaldson. I'll dig up the build sheet this coming weekend and list the RPO code. I replaced the air cleaner with an open type in 1975 when I did the Holley conversion.

As promised the RPO code on the build sheet to my 68 GMC for the air cleaner is K-48